Reproductive techniques (i.e., artificial insemination, in vitro fertilization, embryo transfer and cloning) find their greatest application in understanding species uniqueness, adaptations and physiological mechanisms, not in the large-scale assisted breeding and the production of offspring. Models of how to use these tools to study reproductive fitness are emerging to help insure gene diversity and even propagate endangered species, but only after fundamental databases have been developed. Non-invasive hormone metabolite monitoring, artificial insemination and genome resource banking are being used in situ and ex situ to understand wildlife biology. We predict that as the fundamental, multi-species database grows, so will the applied benefits for: (1) developing genome banks for insuring extant genetic diversity; (2) assessing the relationship of physiology, behavior and environmental perturbations; (3) managing small populations; and (4) dealing with dilemmas ranging from contraception to skewed sex ratios to animal welfare. Most progress will be made in using these tools in systematic studies to solve the mystery of how thousands of unstudied species reproduce. Understanding gamete biology enhances the ability to commonly reproduce genotypes commonly used as models for human diseases as well as to propagate endangered species. Animal Models for AIDS - AIDS, Animal models, artificial insemination, embryo transfer, Felidae, gene mapping, in vitro fertilization, - Neither Human Subjects nor Human Tissues